1. The Field of the Invention
The present invention relates to skis for enhancing the flotation and steering response of powered snow machines. More particularly, the present invention relates to skis with a channel or other contours on a gliding surface at the bottom thereof and grooves formed within the contours for increasing the flotation ability, steering response, and turning ability of the ski.
2. The Relevant Technology
Technology has made it possible to travel off-road during winter, even in very remote areas. Current machines for traveling over snow, such as snowmobiles, for example, provide the ability to travel swiftly and safely in back-country locations where the terrain is quite rugged. Water sports industries such as recreational vehicle sales and rentals and tourism are growing rapidly as a consequence of this new technology. Industry and rescue operations are also benefitting greatly.
Snow machines continue to be refined and improved. For instance, in the case of snowmobiles, improved performance and reliability allows operators to travel swiftly, safely, and comfortably into secluded regions otherwise inaccessible in winter and in some cases in summer also. Other technological advances, such as increased traction and power and weight reduction, are allowing snowmobiles to be operated in snow depths and mountains slopes of a steepness previously unthinkable.
The snowmobile is a light and agile tracked snow machine that is intended primarily for recreational operation by one or two persons. The small size, lightness, and high power output of these machines makes them highly responsive to shifts in weight and other operator inputs. Using tracks with large lugs and high powered engines, these machines can go faster over trails and deeper in rugged terrain than larger snow machines such as the dual tracked, multiple passenger vehicles currently available. The ruggedness of snowmobiles allows operators to travel over the snow safely at speeds impossible to match by wheeled vehicles in summer and to travel directly to any desired point by "as-the-crow-flies" navigation.
Typically, a snowmobile comprises a long rubberized track about 3 or 4 feet in length. The snowmobile is driven by an engine and the power is applied to the track with the use of a centrifugal clutch. Unlike dual-tracked snow machines, the snowmobile track does not extend entirely to the front of a snowmobile. Instead, the front of the machine rests on one or two specially adapted skis. The skis are attached to the steering mechanism of the snowmobile which may be provided with suspension components to handle bumps. With the use of the handle bars, the operator is able to alter the facing of the skis. Turning the skis in a selected direction generally causes the snowmobile to follow the selected direction of travel of the skis and turn in that direction.
It is believed by the inventors that the skis are a critical component to the steering, tracking, and flotation ability of the snowmobile. As snowmobiles have improved in other aspects, it is believed that the ability of the skis to provide flotation, properly control the snowmobile, and maintain an intended direction of travel have lagged behind.
Conventional snowmobile skis are designed under the notion that to provide the highest degree of speed and flotation, the ski must be smooth and relatively flat. Thus, conventional snowmobile skis are typically smooth and flat. A single shallow keel or wear bar is typically provided extending along the center of the ski to exert a lateral shear force against the snow when the ski is turned, forcing the ski to adhere to an intended direction of travel.
Such an arrangement works at lower speeds and in relatively packed snow. Nevertheless, as speeds increase, and/or as the snow becomes increasingly light and powdery, the shear force exerted by the ski against the snow when turning becomes insufficient to overcome the inertia of the snowmobile.
Consequently, when the conventional snow machine skis are turned in a direction other than the direction of travel of the snow machine to which they are fitted, a high degree of lateral slippage frequently occurs. The sliding of the conventional skis in the original direction of travel is termed "pushing." Pushing makes it difficult to traverse steep terrain and can make even normal trail operation of the snow machine dangerous.
Due to the tendency to push, snowmobiles with conventional skis must be directed straight up the face of a steep slope, rather than traversing it. In attempting to traverse less steep hills, a skilled operator can often keep the snowmobile upright and maintaining an intended direction of travel to some degree, but the skis still often fail to hold a straight course and may slide sideways, down the hill. When this occurs, the snowmobile may tip over, unseating the operator and possibly rolling out of control down the hill.
Additionally, when attempting to turn the snowmobile sharply on even packed surfaces when traveling at a high rate of speed, the skis can break loose suddenly, throwing the snowmobile off the trail. This can result in the snowmobile crashing into trees, snow banks, or other objects.
A further characteristic of conventional snow machine skis is the tendency to sink through soft, top layers of snow and catch on underlying ruts or other sharp contours in the path of the snow machine. This digression from the intended course is referred to as "darting." Darting, like pushing, can make it very difficult to maintain control of the snow machine, especially at high speeds. One main reason that darting occurs is that the conventional single keel skis tend to seek the same tracks as skis that have previously passed down the trail. Highly traveled trails can be covered with such tracks. Conventional skis tend to seek the tracks, and may jump or dart back and forth seeking first one set of tracks, and then a second, third, etc.
Conventional skis also exhibit shortcomings in the area of flotation in deep powdered snow. Typically, in such snow conditions, a high rate of speed can keep the snowmobile planing at the surface. However, on steep slopes that are covered with snow that is powdery and light so as to fail to provide a packable base to support the snowmobile below a certain speed, the snowmobile often loses its momentum. In such a case, the skis will begin to sink into the snow. When this occurs, the track begins to dig a trench. Unless the snowmobile regains its momentum, the trench will continue to grow until the snowmobile becomes firmly stuck. Such a situation can be very dangerous, as the operator may become stranded.
Thus, as technological barriers are being overcome, certain limitations of current snow machines have come glaringly to light. To fully utilize current technological benefits, snowmobiles must be provided with increased flotation ability, steering ability, and tracking capability. Until these needs are met, much terrain will remain impassible or at least dangerous to the operators of snow machines.
One problem with attempting to concurrently increase both the flotation and turning ability of a snowmobile ski is that the two re often antithetical to each other. That is, a broader, flatter ski is known to be desirable for flotation, while a narrower and deeper ski with sharp edges is desired for greater turning ability. Thus, the inventors have recognized a need for a ski with increased shear force for greater turning ability and steering response, but while still maintaining low friction and high flotation ability.
Such a ski would be even more useful if able to overcome the problems mentioned above of pushing and darting. If such as ski could be used to provide high floatation in powder snow and also provide improved steering on packed and groomed surfaces, the ski would be a great improvement in the art, complementing the technological advances already made. Such a ski would provide increased winter access to rugged terrain, greater enjoyment to consumers, and greater safety for those traveling off-road in winter.